A prediction model for concentration of gaseous pollutants in deeply buried water pipelines under longitudinal ventilation

Abstract This study investigates the diffusion mechanism of gaseous pollutants within the water pipeline under longitudinal ventilation by analyzing the effects of ventilation velocity, release rate, and distance to the air inlet vent. According to previous studies, NH 3 was chosen as the gaseous pollutant, and a series of numerical simulations were conducted. The results demonstrate that the airflow within the water pipeline is piston flow, the direction of which is determined by ventilation mode. Affected by the Coanda effect, the ununiform velocity leads to an uneven distribution of NH 3 on the water pipeline cross‐sections. The mean cross‐sectional values are chosen for further analysis. The concentration of NH 3 in the water pipeline is proportional to the release rate of NH 3 and distance to the air inlet vent, respectively. When the release rate is fixed, increasing the ventilation velocity can effectively remove the pollutant, and the concentration of NH 3 is proportional to the −1 power of the ventilation velocity. Finally, a prediction model of the mean cross‐sectional concentration of NH 3 is obtained by combining it with theoretical analysis. Therefore, this study can not only optimize the operation of the ventilation system in this Inter‐basin Water Transfer (IBWT) project but also guide the design of the ventilation system in other IBWT projects with deep buried long‐distance water pipelines.